The invention relates to a rotary piston internal combustion engine of the trochoidal type with a housing which comprises at least one peripheral wall portion and at least two parallel side portions and has induction and exhaust ports. Each peripheral wall portion and two associated side portions defines a cavity in which a muli-apex piston is rotatably mounted to define variable volume working chambers. The piston is provided with seal elements which are in sliding engagement with the inner surfaces of the housing. A passage is provided in the housing for lubricating these inner surfaces. The passage opens into the cavity in the neighbourhood of each induction port in the region of that working chamber which is undergoing the induction phase. The passage is in communication with the atmosphere and a lubricant feed pump opens into the passage.
One known engine of the this type is present in British Patent No. 1,422,087. In that engine, a uniformly dosed supply of lubricant to the inner surfaces of the housing and to the seal elements that are in sliding contact with it is achieved by arranging that the lubricant entering the passage is picked up by the air flow past it. As a consequence of its adhesion, the walls of the passage are coated with a film of lubricant which is uniformly driven forwards into the working chamber. The passage in this arrangement has a special variable air-throttling device which is coupled to the throttle valve of the engine and which, when the throttle valve is closed, uncovers a small cross sectional area and with progressive opening of the throttle valve it uncovers a progressively greater cross sectional area. The degree of effectiveness of the air stream in driving the lubricant forward can thereby be increased or decreased according to the position of the engine throttle. Thereby a corresponding quantity of lubricant, delivered for example from a metering pump, is driven forward to a greater or lesser extent, and also the danger is avoided of a substantial quantity of lubricant entering the chamber suddenly and being burnt up unused. A non-return valve is provided in the lubricant feed pipe so that the lubricant feed pipe that opens into the passage is not sucked dry by high vacuum prevailing in the working chamber and so that the subsequent supply of lubricant cannot be interrupted. It is true that this arrangement does ensure correct lubrication of the sealing elements to match the prevailing working conditions, however, there is a constant need in the art for improvement in lowering the equipment costs for the type of system under consideration.